The dimple that forms under your belly button because you got fat.
"awe, you have a dimple in your fat"
"yes, that's my fimple"
(N) a mysterious person who shows up on your facebook friends list and you have no idea where they came from or who they are; are known as 'fimples'. Removing said person is known as "popping a fimple".
A fimple just popped up on my facebook friends list.